Ice-making machine and heat exchanger therefor

ABSTRACT

An ice-making machine includes a housing having a brine solution inlet to receive brine solution from which ice is to be made and having an ice-brine slurry outlet to permit the egress of an ice-brine slurry from the housing. A heat exchanger within the housing has a heat exchange surface. The heat exchanger further includes a refrigerant inlet, a refrigerant outlet and at least one refrigerant circuit interconnecting the refrigerant inlet and the refrigerant outlet to permit a flow of refrigerant through the heat exchanger to extract heat from the brine solution contacting the heat exchange surface. The at least one refrigerant circuit is constituted by refrigerant passages integrally formed in a body portion of the housing. A blade assembly within the housing carries a plurality of blades each of which is in contact with the heat exchange surface. The blade assembly is mounted on a shaft which is rotatable by a motor to move the blades across the heat exchange surface to remove cooled fluid therefrom and inhibit the deposition of ice crystals on the heat exchange surface.

FIELD OF THE INVENTION

The present invention relates to ice-making machines and in particularto an ice-making machine having a heat exchanger body with integrallyformed refrigerant passages therein and to a heat exchanger therefor.

BACKGROUND OF THE INVENTION

Ice-making machines are well known in the art and many designs have beenconsidered. For example, Applicant's U.S. Pat. No. 4,796,441 issued onJan. 10, 1989 discloses an ice-making machine having a chamber with afluid inlet to receive a brine solution from which ice is to be made anda fluid outlet to permit the egress of an ice-brine slurry from thehousing. The interior surface of the chamber defines a heat exchangesurface. A blade assembly is mounted on a rotatable shaft extendingthrough the centre of the chamber. The blade assembly is in contact withthe heat exchange surface. A motor rotates the shaft at a rate such thatthe interval between successive passes of the blade assembly over theheat exchange surface is such so as to inhibit the formation of icecrystals on the heat exchange surface.

A tubular jacket surrounds the chamber. A refrigerant inlet and arefrigerant outlet communicate with the space between the jacket andchamber and are positioned at opposed ends of the ice-making machine.Refrigerant flowing from the inlet to the outlet boils and in so doing,cools the brine solution in contact with the heat exchange surface.Refrigerant leaving the ice-making machine via the outlet is compressedbefore being fed back to the inlet. Rings are welded to the jacket atlaterally spaced locations to provide structural stability to theice-making machine allowing it to withstand internal pressures. Althoughthis ice-making machine works satisfactorily, it is time consuming andexpensive to manufacture. Accordingly, improved but less expensiveice-making machines with increased efficiency are continually beingsought.

It is therefore an object of the present invention to provide a novelice-making machine and a heat exchanger therefor.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided anice-making machine comprising:

a housing having an inlet to receive a fluid from which ice is to bemade and an outlet to permit the egress of ice from said housing;

a heat exchanger within said housing having at least one heat exchangesurface, said heat exchanger further including a refrigerant inlet, arefrigerant outlet and at least one refrigerant circuit interconnectingsaid refrigerant inlet and said refrigerant outlet to permit a flow ofrefrigerant through said heat exchanger to extract heat from fluidcontacting said at least one heat exchange surface, said at least onerefrigerant circuit being constituted by refrigerant passages integrallyformed in a body portion said housing;

blade means in contact with said at least one heat exchange surface andmovable about an axis to move across said at least one heat exchangesurface and remove cooled fluid therefrom; and

drive means to move said blade means across said at least one heatexchange surface.

In a preferred embodiment, the heat exchanger includes a plurality ofrefrigerant circuits, each of which is connected to the refrigerantinlet and outlets and is constituted by a plurality of refrigerantpassages formed in the housing. It is preferred that the cross-sectionalarea of the refrigerant passages in each of the refrigerant circuitsincreases from the refrigerant inlet to the refrigerant outlet.Furthermore, it is preferred that the refrigerant passages arepositioned in the refrigerant circuits relative to one another toequalize heat exchange between the fluid and the refrigerant along therefrigerant circuits.

According to another aspect of the present invention there is providedan ice-making machine comprising:

a housing having an inlet to receive a fluid from which ice is to bemade and having an outlet to permit the egress of ice from said housing;

a heat exchanger within said housing having at least one heat exchangesurface, said heat exchanger further including a refrigerant inlet, arefrigerant outlet and at least one refrigerant circuit interconnectingsaid refrigerant inlet and said refrigerant outlet to permit a flow ofrefrigerant through said heat exchanger to extract heat from fluidcontacting said at least one heat exchange surface, said at least onerefrigerant circuit increasing in cross-sectional dimension from saidrefrigerant inlet to said refrigerant outlet;

blade means in contact with said at least one heat exchange surface andmovable about an axis to move across said at least one heat exchangesurface and remove cooled fluid therefrom; and

drive means to move said blade means across said at least one heatexchange surface.

According to still yet another aspect of the present invention there isprovided an ice-making machine comprising:

a housing having an inlet to receive a fluid from which ice is to bemade and having an outlet to permit the egress of ice from said housing;

a heat exchanger within said housing having at least one heat exchangesurface, said heat exchanger further including a refrigerant inlet, arefrigerant outlet and at least one refrigerant circuit interconnectingsaid refrigerant inlet and said refrigerant outlet to permit a flow ofrefrigerant through said heat exchanger to extract heat from fluidcontacting said at least one heat exchange surface;

blade means in contact with said at least one heat exchange surface andmovable about an axis to move across said at least one heat exchangesurface and remove cooled fluid therefrom, said blade means including ablade carrier having a plurality of circumferentially spaced fluidpassages therethrough to direct fluid entering said housing via saidinlet towards said at least one heat exchange surface; and

drive means to move said blade means across said at least one heatexchange surface.

According to still yet another embodiment of the present invention thereis provided an ice-making machine comprising:

a housing having an inlet to receive a fluid from which ice is to bemade and having an outlet to permit the egress of ice from said housing;

a heat exchanger within said housing having at least one heat exchangesurface, said heat exchanger further including a refrigerant inlet, arefrigerant outlet and at least one refrigerant circuit interconnectingsaid refrigerant inlet and said refrigerant outlet to permit a flow ofrefrigerant through said heat exchanger to extract heat from fluidcontacting said at least one heat exchange surface;

blade means in contact with said at least one heat exchange surface andmovable about an axis to move across said at least one heat exchangesurface and remove cooled fluid therefrom, said blade means including ablade carrier having a plurality of equally spaced circumferentiallydisposed blades thereon contacting said heat exchange surface, saidblades being flexibly mounted on said blade carrier and pivoting towardssaid blade carrier in the event of ice accumulation on said heatexchange surface, said blade means also including and scraper elementson said blade carrier and being spaced from said at least one heatexchange surface, said scraper elements scrapping ice accumulated onsaid at least one heat exchange surface to limit accumulation thereof;and

drive means to move said blade means across said at least one heatexchange surface.

According to still yet another aspect of the present invention there isprovided a heat exchanger for an ice-making machine comprising:

a generally cylindrical body having an interior surface constituting aheat exchange surface; and

at least one refrigerant circuit constituted by a plurality ofrefrigerant passages integrally formed in said body.

The present invention provides advantages in that since the body of theheat exchanger is extruded and is formed with integral refrigerantpassages, the ice-making machine is less expensive to manufacture, easyto assemble and can be mass produced. Also, the modular design of theice-making machine allows a plurality of ice-making machines to beinterconnected to achieve the desired capacity while maintainingindividual refrigerant and/or brine solution inlets and outlets. Inaddition, the present invention provides advantages in that fine iceparticles in a brine solution can be made efficiently by increasing andequalizing heat transfer between the brine solution and the refrigerantover basically the entire heat exchange surface within the ice-makingmachine. In a particular embodiment, this is achieved by increasing thecross-sectional area of the refrigerant passages in the refrigerantcircuits along their length from the refrigerant inlet to therefrigerant outlet and by positioning the refrigerant passages in therefrigerant circuits relative to one another to equalize heat exchangebetween the fluid and the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described more fullywith reference to the accompanying drawings in which:

FIG. 1 is a cross-sectional view of an ice-making machine in accordancewith the present invention;

FIG. 2 is a cross-sectional view of the body of the ice-making machineheat exchanger taken along the line 2--2 in FIG. 1;

FIG. 3 is an end view of a gasket forming part of the ice-making machineof FIG. 1;

FIG. 4 is an end view of a blade assembly forming part of the ice-makingmachine of FIG. 1 taken in the direction of arrow 5;

FIG. 5 is a perspective view of the blade assembly of FIG. 4;

FIG. 6 is a perspective view of the portion of FIG. 3 showing theinterconnections between refrigerant passages in a refrigerant circuitwithin the ice-making machine of FIG. 1;

FIG. 7 is a schematic of the ice-making machine of FIG. 1 connected toan ice-brine slurry recirculation circuit;

FIG. 8 is a front elevational view of a plurality of stacked ice-makingmachines in accordance with the present invention; and

FIG. 9 is a side elevational view of the stacked ice-making machines ofFIG. 8 taken in the direction of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, an ice-making machine is shown and is generallyindicated to by reference numeral 10. As can be seen, ice-making machine10 includes a generally cylindrical housing 12 constituted by acylindrical central body portion 14 and a pair of end plates 16 and 18respectively secured to the ends of the central body portion 14 bysuitable fasteners (not shown). Gaskets 20 (best seen in FIG. 3) arepositioned between the end plates 16 and 18 and the central body portion14 to seal the housing 12 and inhibit fluid leakage.

FIGS. 1, 2 and 6 best illustrate the central body portion 14. As can beseen, the central body portion 14 is of a single piece constructionformed from extruded aluminum and includes a cylindrical interiorsurface 30 which defines the heat exchange surface of the ice-makingmachine 10. The heat exchange surface 30 is coated with a corrosion anderosion resistant agent. The corrosion and erosion resistant agent is inturn coated with a release agent such as Teflon® to inhibit thedeposition of ice crystals thereon.

A plurality of refrigerant circuits 32, in this example four,constituted by refrigerant passages 34, are integrally formed within thecentral body portion 14 and are circumferentially spaced about thecentral body portion. Each refrigerant circuit 32 includes a pluralityof refrigerant passages 34, in this case five which are labelled #1 to#5. The cross-sectional area of each of the refrigerant passages 34 ineach refrigerant circuit 32 is different.

Specifically, the #1 and #2 refrigerant passages 34 are elliptical andhave major axes aligned with radial lines extending from the center ofthe central body portion 14. The #3 refrigerant passages 34 arecircular. The #4 and #5 refrigerant passages 34 also are elliptical.However, the major axes of these refrigerant passages are tangential tothe heat exchange surface 30. As can be seen, the #1 refrigerantpassages have the smallest cross-sectional area. The cross-sectionalarea of the refrigerant passages 34 increases with the assigned notationso that the #5 refrigerant passages have the largest cross-sectionalarea. The elliptical cross-section of the #1, #2, #4 and #5 refrigerantpassages 34 increases the surface area of the refrigerant passages ascompared with circular passages and thereby increases heat transferbetween fluid contacting the heat exchange surface 30 and refrigerantflowing through the refrigerant passages 34. This of course increasesthe efficiency of the ice-making machine. As one of skill in the artwill appreciate, other refrigerant passage cross-sections can beselected to increase the surface area of the refrigerant passages.

The interior of each refrigerant passage 34 is preferably designed tocreate turbulence as refrigerant flows through the refrigerant circuits32 to enhance boiling of the refrigerant. In this particular embodiment,this is achieved by providing a turbulent creating structure on theinterior surfaces 36 of the refrigerant passages 34. Although not shown,it is preferred that the turbulent creating structure is in the form ofsmall trapezoidal fins on the interior surfaces 36, referred to asmicrofins.

The spacing between adjacent refrigerant passages 34 in each of therefrigerant circuits 32 and the good thermal conductivity of thealuminum central body portion 14 allows heat transfer between therefrigerant circulating through the refrigerant passages 34 and brinesolution contacting the heat exchange surface 30 to occur aboutgenerally the entire circumference of the refrigerant passages 34 andnot just the portion of the refrigerant passage walls proximal to theheat exchange surface 30. This allows the efficiency of the ice-makingmachine 10 to be increased.

Referring now to FIGS. 1 and 6, the end plates 16 and 18 are betterillustrated. The end plates 16 and 18 in this embodiment are annular andare formed in two pieces. If desired, the end plates may be casted as asingle piece. Each end plate 16, 18 includes a central insert 16a, 18aformed of plastic material and an outer annular aluminum flange 16b, 18bsurrounding and secured to the plastic insert 16a, 18a by suitablefasteners (not shown). The end plates 16, 18 are bolted to opposed endsof the central body portion 14.

The outer flange 16b of end plate 16 has four refrigerant inlets 50integrally formed therein, two of which are shown in FIG. 1. Eachrefrigerant inlet 50 is connected to the #1 refrigerant passage 34 of adifferent refrigerant circuit 32 and receives a flow of refrigerant.Interconnect passages 54 are also formed in the outer flange 16b of endplate 16 and interconnect the #2 and #3 refrigerant passages 34 and the#4 and #5 refrigerant passages 34 of each refrigerant circuit 32.

The outer flange 18b of end plate 18 has four refrigerant outlets 60formed therein, two of which are shown in FIG. 1. Each refrigerantoutlet 60 is connected to the #5 refrigerant channel 34 of a differentrefrigerant circuit 32 and allows the refrigerant to exit the ice-makingmachine 10. Interconnect passages 64 are also formed in the outer flange18b of end plate 18 to interconnect the #1 and #2 refrigerant passages34 and the #3 and #4 refrigerant passages 34 of each refrigerant circuit32. FIG. 6 illustrates the interconnections between the refrigerantpassages 34 in one of the refrigerant circuits 32 as established by theinterconnect passages 54 and 64 respectively.

The central insert 18a of end plate 18 includes a brine solution inlet66 and an ice-brine slurry outlet 68 to permit the ingress of a brinesolution or ice-brine slurry into the ice-making machine 10 and topermit the egress of an ice-slurry brine from the ice-making machine 10.The brine solution inlet 66 co-operates with a hollow shaft 70 extendingfrom the end plate 18 and partially into the central body portion 14. Abushing 72 on the end plate 18 allows the hollow shaft 70 to rotateabout its longitudinal axis relative to the end plate 18.

A drive shaft 80 extends through the central insert 16a of end plate 16and partially into the central body portion 14 before terminating at apointed end 82 near the open end of the hollow shaft 70. Bushings 84 onthe end plate 16 allow the drive shaft 80 to be rotated about itslongitudinal axis by way of a motor (not shown) relative to the endplate 16. A seal 86 acts between the central insert 16a of end plate 16and the shaft 80 to inhibit fluid leakage.

A blade assembly 90 (best seen in FIGS. 1, 4 and 5) is mounted on thehollow, shaft 70 and drive shaft 80 and includes a cylindrical bladecarrier 92 through which three circumferential spaced, inclined,generally ovate passages 94 are provided. One end of each passage 94 isin fluid communication with the open end of the hollow shaft 70 whilethe opposite end of each passage 94 is positioned to discharge brinesolution towards the heat exchange surface 30. The passages 94 arespaced 120° about the blade carrier 92 to balance the load placed on theshaft 82 as brine solution flows along the passages 94. The radialspacing 95 between the outer surface of the blade carrier 92 and theheat exchange surface 30 is small, in this example 1/4 inch, to maintainhigh velocity brine solution flow through the ice-making machine 10 andinhibit the formation of ice crystals on the heat exchange surface 30.

The blade carrier 92 has a plurality of equi-circumferentially spaced,longitudinal keyed slots 96 formed in its outer surface. Each keyed slot96 receives a plurality of blades 98 separated by spacers 100. Thearrangement of blades 98 and spacers 100 along each slot 96 is such thatthe blades 98 accommodated by the various slots 96 are longitudinallyoffset but slightly overlap. Since the blades 98 are spaced about theblade carrier 92 by approximately 120° and are in contact with the heatexchange surface 30, the blades 98 help to center the shaft 82 withrespect to the housing 12. Springs 102 act between the blades 98 at theends of the slots and the spacers 100 to push the blades 98 towards therespective end plates 16, 18.

Each blade 98 includes a flexible body 104 having one end 106 of a shapecomplimentary to the keyed slots 96. The free end 108 of the body 104terminates in a hook 110 defining an edge 112 to contact and rideagainst the heat exchange surface 30. The blade 98 may be in the form ofa composite with the hook 110 being formed of more rigid material thanthe flexible body 104. Alternatively, the blade 98 may be formed from asingle rigid material and profiled to allow the body 104 to flex in thedesired manner. The top surfaces of the spacers 100 are serrated todefine scraper elements 116.

Referring now to FIG. 7, the ice-making machine 10 is shown connected toan ice-making system. As can be seen, the refrigerant inlets 50 areconnected to the outlet of a condenser unit 120 by way of an inletheader (not shown). The refrigerant outlets 60 are connected to theinlet of the condenser unit 120 by way of an outlet header (not shown).The condenser unit 120 condenses and compresses refrigerant exiting theice-making machine 10 by way of the refrigerant outlets 60 beforerecirculating the refrigerant to the refrigerant inlets 50. Theice-brine slurry outlet 68 is connected to a discharge conduit 122.Discharge conduit 122 leads to an outlet 124 as well as to arecirculation conduit 126. Recirculation conduit 126 leads to an inletconduit 128 which also receives brine solution. The inlet conduit 128supplies brine solution and/or ice-brine slurry to the brine solutioninlet 66. A pump 130 is positioned along the recirculation conduit 126to recirculate ice-brine slurry. The amount of brine solution enteringthe inlet conduit 128 and mixing with the recirculated ice-brine slurrycan be controlled to allow the ice fraction of ice-brine slurry producedin the ice-making machine 10 to be adjusted as desired.

The operation of the ice-making machine 10 will now be described. Inoperation brine solution or ice-brine slurry (hereinafter referred to asbrine solution) is fed into the ice-making machine 10 through the brinesolution inlet 66. The brine solution flows through the hollow shaft 70and is then directed by the pointed end 82 of the drive shaft 80 towardsthe three inclined passages 94. The brine solution flows along the threeinclined passages 94 until the brine solution exits the blade carrier 92adjacent the heat exchange surface 30. While this is occurring,refrigerant enters each of the refrigerant circuits 32 by way of therefrigerant inlets 50. The refrigerant flows along the refrigerantpassages 34 of each refrigerant circuit 32 and exits the refrigerantcircuits 32 via the refrigerant outlets 60. As the refrigerant flowsthrough the refrigerant passages 34 in the central body portion 14, therefrigerant absorbs heat through the heat exchange surface 30 and boils.The brine solution in contact with the heat exchange surface 30 is thussupercooled.

To avoid deposition of ice on the heat exchange surface 30 which wouldinhibit heat transfer to the refrigerant and thereby reduce theefficiency of the ice-making machine 10, the blade assembly 90 isrotated by the motor driven drive shaft 80. Specifically, the bladeassembly 90 is rotated at a rate of speed that is fast enough to allowthe blades 98 to remove the supercooled brine solution from the heatexchange surface 30 prior to crystallization of ice crystals on the heatexchange surface 30. The supercooled brine solution thereforecrystallizes in the brine solution between the blade carrier 92 and theheat exchange surface 30 allowing the brine solution to act as asecondary refrigerant in the formation of fine ice crystals throughoutthe brine solution.

The flexible nature of the blade bodies 104 allows the blades to conformto the heat exchange surface 30 as the blades 98 are rotated. If a layerof ice should inadvertently form on the heat exchange surface 30, theblades 98 will flex until they overlie the outer surface of the bladecarrier 92. When this occurs, the scraper elements 116 project radiallybeyond the blades 98 allowing the scraper elements 116 to scrape the icelayer and avoid damage to the blades 98.

The small radial spacing 95 between the blade carrier 92 and the heatexchange surface 30 ensures high velocity brine solution flow from thepassages 94 to the ice-brine slurry outlet 68 in the end plate 18. Thisfurther assists to inhibit the formation of ice crystals on the heatexchange surface 30.

In order to increase efficiency of the ice-making machine 10, therefrigerant passages 34 in each refrigerant circuit 32 increase incross-sectional area along the length of the refrigerant circuit. Theincreased cross-sectional area maintains a high velocity of refrigerantas the refrigerant circulates through the refrigerant circuits 32 whileavoiding a high pressure drop along the length of the refrigerantcircuits 32 helping to increase the efficiency of the ice-makingmachine. In addition, the staggered arrangement of the variousrefrigerant passages 34 in each refrigerant circuit 32 helps to equalizeheat transfer over the circumference of the central body portion 14 andthereby maintain a uniform temperature within the ice-making machine 10.Moreover, the microfin structure on the interior surfaces 36 of therefrigerant passages 34 enhances boiling of the refrigerant therebyimproving its heat transfer ability.

As those of skill in the art will appreciate, the present ice-makingmachine allows fine ice particles in a brine solution to be madeefficiently by increasing and equalizing heat transfer between the brinesolution and the refrigerant over basically the entire heat exchangesurface.

Although the end plate 18 has been described as having the brinesolution inlet and the ice-brine slurry outlet provided therein, thebrine solution inlet and ice-brine slurry outlet can be provided in endplate 16 or the brine solution inlet can be provided in one end plateand the ice-brine slurry outlet can be provided in the other end plate.Also, although end plate 16 is shown to include the refrigerant inletsand end plate 18 is shown to include the refrigerant outlets, theposition of the refrigerant inlets and outlets can be reversed. Also,both the refrigerant inlets and refrigerant outlets can be formed ineither the end plate 16 or end plate 18 if desired.

Referring now to FIGS. 8 and 9 another embodiment of an ice-makingmachine in accordance with the present invention is shown. In thisembodiment, like reference numerals will be used to indicate likecomponents with a suffix "'" added for clarity. As can be seen, aplurality of ice-making machines 10' are stacked in an array. In thisembodiment, the outer flanges 16b', 18b' of the end plates 16', 18' arehexagonal allowing the ice-making machines 10' to be nested. Therefrigerant inlets 50' in the end plates 16' are arranged in pairs. Eachpair of refrigerant inlets 50' is connected to a refrigerant conduit 200extending between opposed sides of the end plates 16'. The open ends ofthe refrigerant conduits 200 are aligned with the refrigerant conduits200 in the end plates 16' of adjacent ice-making machines 10'. O-ringseals 202 act between adjacent ice-making machines 10' to inhibitrefrigerant leakage. A base 204 is attached to the end plate 16' of thebottom ice-making machine 10' of each stack to seal one end of therefrigerant conduits 200. An inlet header 206 is attached to the endplate 16' of the top ice-making machine 10' of each stack to receive aflow of refrigerant and allow the refrigerant to be delivered to each ofthe ice-making machines 10' in the stack.

The end plates 18 are of a similar design to allow refrigerant exitingthe refrigerant circuits in each of the ice-making machines 10' to befed to refrigerant conduits. The refrigerant conduits in the end plates18 of the ice-making machines 10' in each stack are interconnected andlead to an outlet header attached to the top ice-making machine 10' ineach stack.

Although not shown, the end plates 16' and 18' can also be designed toinclude a similar arrangement for the brine solution inlet and ice-brineslurry outlet. This modular design of the ice-making machines allows theice-making machines to be arranged in an array of a size selected toproduce ice-brine slurry at the desired capacity.

Although the refrigerant passages have been described as being coatedwith a corrosion and erosion resistant agent and receiving the flow ofrefrigerant directly, the refrigerant passages and interconnect passagescan be lined with tubing if desired to accommodate the flow ofrefrigerant along the refrigerant circuits.

Although specific embodiments of the present invention have beendescribed, those of skill in the art will appreciate that variations andmodifications may be made to the present invention without departingfrom the scope thereof as defined by the appended claims.

I claim:
 1. An ice-making machine comprising:a housing having an inletto receive a fluid from which ice is to be made and an outlet to permitthe egress of ice from said housing; a heat exchanger forming part ofsaid housing having at least one solid body portion defining at leastone heat exchange surface, said heat exchanger further including arefrigerant inlet, a refrigerant outlet and at least one refrigerantcircuit interconnecting said refrigerant inlet and said refrigerantoutlet to permit a flow of refrigerant through said heat exchanger toextract heat from fluid contacting said at least one heat exchangesurface, said at least one refrigerant circuit being constituted bygenerally parallel refrigerant passages extending longitudinally throughsaid at least one solid body portion at spaced locations; blade means incontact with said at least one heat exchange surface and movable aboutan axis to move across said at least one heat exchange surface andremove cooled fluid therefrom; and drive means to move said blade meansacross said at least one heat exchange surface.
 2. An ice-making machineas defined in claim 1 wherein said heat exchanger includes a pluralityof refrigerant circuits, each of said refrigerant circuits beingconnected to said refrigerant inlet and to said refrigerant outlet, eachof said refrigerant circuits being constituted by a plurality ofrefrigerant passages formed in said body portion.
 3. An ice-makingmachine as defined in claim 2 wherein said housing includes a unitary,hollow solid body defining a generally cylindrical interior heatexchange surface, said refrigerant passages extending longitudinallythrough said body at circumferentially spaced locations generally aboutthe entire circumference of said body.
 4. An ice-making machine asdefined in claim 3 wherein the cross-sectional area of the refrigerantpassages in each of said refrigerant circuits is different, successiverefrigerant passages having a greater cross-sectional area.
 5. Anice-making machine as defined in claim 4 wherein successive refrigerantpassages in each of said refrigerant circuits are positioned relative toone another to equalize heat exchange between fluid contacting said heatexchange surface and refrigerant flowing successively through saidrefrigerant passages.
 6. An ice-making machine as defined in claim 5wherein said body is of a one-piece construction formed of extrudedaluminium and wherein said heat exchange surface is coated with acorrosion and erosion resistant agent.
 7. An ice-making machine asdefined in claim 6 wherein said refrigerant circuits include means toenhance boiling of said refrigerant.
 8. An ice-making machine as definedin claim 3 wherein said housing further includes a pair of end platesfastened to opposed ends of said generally cylindrical body, one of saidend plates accommodating said refrigerant inlet and the other of saidend plates accommodating said refrigerant outlet, said end platesfurther including interconnect passages to interconnect successiverefrigerant passages in said refrigerant circuits.
 9. An ice-makingmachine as defined in claim 7 wherein said boiling enhancement means isin the form of a fin structure formed on surfaces of said body definingsaid refrigerant passages.
 10. An ice-making machine comprising:ahousing having an inlet to receive a fluid from which ice is to be madeand having an outlet to permit the egress of ice from said housing; aheat exchanger forming part of said housing and having at least onesolid body portion defining a generally cylindrical heat exchangesurface, said heat exchanger further including a refrigerant inlet, arefrigerant outlet and at least one refrigerant circuit interconnectingsaid refrigerant inlet and said refrigerant outlet to permit a flow ofrefrigerant through said heat exchanger to extract heat from fluidcontacting said heat exchange surface, said at least one refrigerantcircuit being constituted by refrigerant passages extendinglongitudinally through said at least one solid body portion at spacedlocations;blade means in contact with said heat exchange surface androtatable about a generally central longitudinal axis of said housing tomove across said heat exchange surface and remove cooled fluidtherefrom, said blade means including a rotatable blade carrier having aplurality of circumferentially spaced fluid passages extendingtherethrough and in fluid communication with said inlet to direct fluidentering said housing via said inlet towards said heat exchange surfaceand generally about its circumference as said blade carrier is rotated;and drive means to move said blade means across said heat exchangesurface.
 11. An ice-making machine as defined in claim 10 wherein saidinlet is positioned adjacent said central longitudinal axis of saidhousing, said fluid passages being angled with respect to said centrallongitudinal axis, each of said fluid passages having one end adjacentsaid inlet and an opposite end adjacent said heat exchange surface. 12.An ice-making machine as defined in claim 11 wherein said blade carriersupports a plurality of circumferentially spaced blades, each being incontact with said heat exchange surface, said blades being flexiblymounted on said blade carrier.
 13. An ice-making machine comprising:ahousing having an inlet to receive a fluid from which ice is to be madeand having an outlet to permit the egress of ice from said housing; aheat exchanger forming part of said housing and having at least onesolid body portion defining a generally cylindrical heat exchangesurface, said heat exchanger further including a refrigerant inlet, arefrigerant outlet and at least one refrigerant circuit interconnectingsaid refrigerant inlet and said refrigerant outlet to permit a flow ofrefrigerant through said heat exchanger to extract heat from fluidcontacting said heat exchange surface, said at least one refrigerantcircuit being constituted by refrigerant passages extendinglongitudinally through said at least one solid body portion at spacedlocations; blade means in contact with said heat exchange surface androtatable about an axis to move across said heat exchange surface andremove cooled fluid therefrom, said blade means including a rotatableblade carrier having a plurality of generally equally spacedcircumferentially disposed blades thereon contacting said heat exchangesurface, said blades being flexibly mounted on said blade carrier andpivoting towards said blade carrier in the event of ice accumulation onsaid heat exchange surface, said blade means also including scraperelements on said blade carrier and being spaced from said at least oneheat exchange surface to scrape ice accumulated on said heat exchangesurface, said scraper elements projecting from said blade carrier asufficient distance to allow said blades to pivot towards said bladecarrier when said scraper elements contact ice accumulated on said heatexchange surface to inhibit said blades from being pinned between iceaccumulated on said heat exchange surface and said blade carrier; anddrive means to move said blade means across said heat exchange surface.14. An ice-making machine as defined in claim 13 wherein said scraperelements are positioned between said blades.
 15. An ice-making machinecomprising:a housing including a tubular main body constituted by atleast one solid body portion and defining a generally cylindrical,internal heat exchange surface, a fluid inlet to receive fluid fromwhich ice is to be made to enable said fluid to contact said heatexchange surface and circulate through said housing, and an outlet topermit the egress of ice from said housing; blade means extendingaxially through said main body and contacting said heat exchangesurface, said blade means being rotatable about a longitudinal axis ofsaid housing to move across said heat exchange surface and remove cooledfluid therefrom; a drive rotating said blade means; and at least onerefrigerant circuit including a refrigerant inlet, a refrigerant outlet,and a plurality of generally parallel refrigerant passagesinterconnecting said refrigerant inlet and said refrigerant outlet, saidrefrigerant passages extending longitudinally through said at least onesolid body portion at circumferentially spaced locations to permit aflow of refrigerant through successive refrigerant passages from saidrefrigerant inlet to said refrigerant outlet to extract heat from fluidcontacting said heat exchange surface.
 16. An ice-making machine asdefined in claim 15 including a plurality of refrigerant circuits, eachof said refrigerant circuits having a refrigerant inlet, a refrigerantoutlet and a plurality of refrigerant passages extending longitudinallythrough said main body at circumferentially spaced locations andgenerally about its entire circumference.
 17. An ice-making machine asdefined in claim 16 wherein the refrigerant passages of each refrigerantcircuit have generally constant but different cross-sectional areas. 18.An ice-making machine as defined in claim 17 wherein each successiverefrigerant passage has a greater cross-sectional area.
 19. Anice-making machine as defined in claim 18 wherein the refrigerantpassages of each refrigerant circuit are positioned relative to oneanother to equalize heat exchange between fluid contacting said heatexchange surface and refrigerant flowing from through said refrigerantpassages from said refrigerant inlet to said refrigerant outlet.
 20. Anice-making machine as defined in claim 19 wherein the spacing betweenadjacent refrigerant passages in each of said refrigerant circuits andthe thermal conductivity of said main body are selected to allow heattransfer between refrigerant circulating through said refrigerantpassages and fluid contacting said heat exchange surface to occurgenerally about the entire circumference of said refrigerant passages.21. An ice-making machine as defined in claim 20 wherein said main bodyis constituted by a single, solid, generally cylindrical body formed ofextruded aluminum, said heat exchange surface being coated with acorrosion and erosion resistant agent.
 22. An ice-making machine asdefined in claim 21 wherein surfaces of said body defining saidrefrigerant passages have a fin structure thereon to enhance boiling ofsaid refrigerant.
 23. An ice-making machine as defined in claim 16wherein said housing includes a pair of end plates fastened to opposedends of said main body, said end plates including interconnect passagesto interconnect successive refrigerant passages in each of saidrefrigerant circuits.
 24. An ice-making machine as defined in claim 23wherein the refrigerant passages in each of said refrigerant circuitsare arranged about the circumference of said body to define outerrefrigerant passages, at least one inner refrigerant passage andintermediate refrigerant passages between said outer refrigerantpassages and said at least one inner refrigerant passage, saidinterconnect passages interconnecting said refrigerant passages so thatrefrigerant flows from said refrigerant inlet through said outerrefrigerant passages, then through said at least one inner refrigerantpassage and then through said intermediate refrigerant passages beforereaching said refrigerant outlet.
 25. An ice-making machine as definedin claim 24 wherein said outer and intermediate refrigerant passageshave an elliptical circumferential configuration and wherein said atleast one inner refrigerant passage has a circular circumferentialconfiguration.
 26. An ice-making machine as defined in claim 25 whereinsaid outer refrigerant passages are oriented so that the major axes oftheir circumferential configurations extend radially with respect tosaid longitudinal axis and wherein said intermediate refrigerantpassages are oriented so that the major axes of their circumferentialconfigurations extend tangential to said heat exchange surface.
 27. Anice-making machine as defined in claim 26 wherein each successiverefrigerant passage of each refrigerant circuit has a greatercross-sectional area.
 28. An ice-making machine as defined in claim 27wherein one of said end plates includes a refrigerant inlet header tosupply refrigerant to each of said refrigerant inlets and wherein theother of said end plates accommodates a refrigerant outlet headerinterconnecting each of said refrigerant outlets.
 29. An ice-makingmachine as defined in claim 16 wherein said blade means includes arotatable blade carrier carrying a plurality of circumferentially spacedblades and having a plurality of circumferentially spaced fluid passagesextending therethrough and in fluid communication with said inlet todirect fluid entering said housing via said inlet towards said at leastone heat exchange surface and generally about its circumference as saidblade carrier is rotated.
 30. An ice-making machine as defined in claim29 wherein said drive means includes a drive shaft extending into saidhousing along said longitudinal axis and a motor to rotate said driveshaft, said blade carrier being generally tubular and defining a centralpassage, said drive shaft extending partially into said central passage,said circumferentially spaced fluid passages being inclined with respectto said longitudinal axis and each having one end adjacent said heatexchange surface and another end in fluid communication with saidcentral passage, said central passage being in fluid communication withsaid inlet.
 31. An ice-making machine as defined in claim 30 whereinsaid circumferentially spaced fluid passages are equally spaced aboutthe circumference of said blade carrier and wherein said another endsare adjacent a distal end of said drive shaft.
 32. An ice-making machineas defined in claim 31 wherein the distal end of said drive shaft isconfigured to direct fluid entering said central passage to saidcircumferentially spaced fluid passages.
 33. An ice-making machine asdefined in claim 29 wherein said circumferentially spaced blades arepivotally mounted on said blade carrier.
 34. An ice-making machine asdefined in claim 33 wherein said blade carrier further includes scraperelements thereon at spaced locations, said scraper elements being spacedfrom said heat exchange surface.
 35. An ice-making machine as defined inclaim 34 wherein said scraper elements project from said blade carrier asufficient distance to allow said blades to pivot towards said bladecarrier when said scraper elements contact ice accumulated on said heatexchange surface to inhibit said blades from being pinned between iceaccumulated on said heat exchange surface and said blade carrier.
 36. Anice-making machine as defined in claim 35 including rows oflongitudinally spaced blades carried by said blade carrier, said rowsextending along said blade carrier at generally equal circumferentiallyspaced locations, the blades in each row being separated by scraperelements.
 37. An ice-making machine as defined by claim 36 wherein theblades in successive rows are longitudinally offset.
 38. An ice-makingmachine as defined by claim 37 further including spring elements actingbetween the scraper elements and blades in each row.
 39. An ice-makingmachine as defined in claim 23 wherein one of said end plates includes arefrigerant inlet header to supply refrigerant to each of saidrefrigerant inlets and wherein the other of said end plates accommodatesa refrigerant outlet header interconnecting each of said refrigerantoutlets, said end plates being configured to allow a plurality of saidice-making machines to be stacked in an array.
 40. An ice-making machineas defined in claim 39 wherein said end plates are generally hexagonal.41. An ice-making machine as defined in claim 40 wherein saidrefrigerant inlet and outlet headers are positioned on said one andother end plates to align with the refrigerant inlet and outlet headersin the end plates of other ice-making machines when said ice-makingmachines are stacked.
 42. An ice-making machine comprising:a housingincluding a tubular main body constituted by at least one solid bodyportion and defining a generally cylindrical, internal heat exchangesurface, a fluid inlet to receive fluid from which ice is to be made toenable said fluid to contact said heat exchange surface and circulatethrough said housing, and an outlet to permit the egress of ice fromsaid housing; blade means extending axially through said main body andcontacting said heat exchange surface, said blade means being rotatableabout a longitudinal axis of said housing to move across said heatexchange surface and remove cooled fluid therefrom; a drive rotatingsaid blade means; and at least one refrigerant circuit including arefrigerant inlet, a refrigerant outlet, and a plurality of refrigerantpassages interconnecting said refrigerant inlet and said refrigerantoutlet, said refrigerant passages extending longitudinally through saidat least one solid body portion at circumferentially spaced locations topermit a flow of refrigerant through successive refrigerant passagesfrom said refrigerant inlet to said refrigerant outlet to extract heatfrom fluid contacting said heat exchange surface, each of saidrefrigerant passages having a different, generally constantcross-sectional area, each successive refrigerant passage having agreater cross-sectional area.
 43. An ice-making machine as defined inclaim 42 including a plurality of refrigerant circuits, each of saidrefrigerant circuits having a refrigerant inlet, a refrigerant outletand a plurality of refrigerant passages extending through said main bodyat circumferentially spaced locations and generally about its entirecircumference.
 44. An ice-making machine as defined in claim 43 whereinsuccessive refrigerant passages in each of said refrigerant circuits arepositioned relative to one another to equalize heat exchange betweenfluid contacting said heat exchange surface and refrigerant flowingsuccessively through said refrigerant passages.
 45. An ice-makingmachine as defined in claim 44 wherein said main body is of a one-piececonstruction formed of extruded aluminum and wherein said heat exchangesurface is coated with a corrosion and erosion resistant agent.
 46. Anice-making machine as defined in claim 45 wherein each of saidrefrigerant passages includes means to enhance boiling of saidrefrigerant.
 47. An ice-making machine as defined in claim 45 whereinsaid housing further includes a pair of end plates fastened to opposedends of said main body, one of said end plates accommodating saidrefrigerant inlet and the other of said end plates accommodating saidrefrigerant outlet, said end plates further including interconnectpassages to interconnect successive refrigerant passages in saidrefrigerant circuits.